On Wednesday, June 22, 2022 at 5:56:14 PM UTC-4, John Harshman wrote:
> On 6/22/22 1:25 PM, Sight Reader wrote:
> > OK, I finally got a chance to watch episode 1 with my family. It says “go to our website to see the science behind the episode” but there’s nothing there but a single video explaining the absolute least controversial thing they show (maybe I was in the wrong part of the website?)
> >
> > Anyway, here are my questions for episode 1, “Coasts”, almost all concerning what sort of evidence has been discovered to support various behaviors and facts displayed in the documentary:
> I think almost everything you ask about here is just speculation for
> which there is no direct evidence and, for most, couldn't be.
> > (1) Evidence MALE T-Rexes raised and cared for offspring rather than females?
> None, to my knowledge.
> > (2) Evidence that an average of 2/3 of an average T-Rex clutch of 15 does not live to maturity (I didn’t know they actually found a T-Rex nest with 15 eggs!)
> Assuming a stable population, that actually seems very liberal. Only two
> of an individual's offspring should live to reproduce, meaning that only
> slightly more than two might live to maturity.
I would expect major ups and downs in a population of recently evolved top predators.
Keep in mind that T-Rex is confined to the upper third of the Maastrichtian,
ca. two million years, yet had a wide range.
So while the "average clutch" would not have a 5-member survival rate, it could happen
for some extended "boom" stages. These might be especially pronounced
as the species was conquering new parts of its final range.
By the way, I would expect most fossils of any animal to be found when the population
was near the peak of a boom stage, so it may not be out of the question for us to
find a fossilized nest of 15 T-Rex eggs.
> > (3) Evidence for how juvenile T-Rexes played (do birds do this and if so, how)?
> No such evidence could likely exist. I know of no evidence for play in
> sibling birds, in or out of the nest. That doesn't mean there isn't any.
> But to extrapolate from living theropods to extinct, giant ones is dubious.
I don't know whether big crocodilians have playful juveniles; do you?
> > (4) Did pterosaurs bear their weight on their (tiny) hind limbs and use their forward limbs mostly as “crutches”? I thought they would have weight on their forelimbs and kinda vault forward (like that vampire bat on a treadmill…)
> Most reconstructions have them walking (not hopping) on four legs.
Peter Wellnhofer's "pterosaur bible" spends much of pages 155-158 discussing pterosaur locomotion on the ground.
With certain specialized exceptions, he comes to the same conclusion.
> > (5) Have we found evidence of large pterosaur colonies on cliff plateaus? Is there evidence that pterosaur hatchlings had an instinct to climb cliffs immediately for protection?
> No. I have no idea what evidence for that could exist.
Wellnhofer writes on p. 157:
"Pterosaurs were adapted to flight to an extreme extent. ...
They must have rested and bred on cliffs and rocks,
where they could hang with their sharp, hook-shaped claws
on hands and feet. To take off, they only needed to
swing themselves into the air. They did not need to
achieve the necessary take-off speed by taking a run on two legs."
My brother-in-law is an expert hang glider, and the last two sentences ring true
from what I've seen him do.
> > (6) Have we found what sorts of stuff pterosaurs burying their eggs in preserve moisture?
> Nothing that I know of.
> > (7) What evidence is there for male plesiosaurs raising their necks high above water as a courtship display?
> No evidence is possible.
However, there might be evidence that it was possible. Of course, the "courtship display" part is purely speculative.
> > (8) What do we know about mosasaur rutting behavior? How deadly was it? They mention finding mosasaur teeth imbedded in other the skulls of others.
> No evidence is possible. Teeth are more reasonably interpreted as predation.
Or self-defense, or a mixture of both. A mammalian example: two stabbing "cats," of genera Nimravus and Eusmilus,
apparently fought each other, perhaps over prey, because the Nimravus skull was found with big holes
that were interpreted as fang marks of an Eusmilus.
> > (9) Is there evidence that ammonite were bioluminescent - that is, had “photocytes”?
> No evidence is possible.
Why not? There have been a number of conclusions from fossil melanosomes of other kinds of animals
for there being various forms of pigmentation.
> > (10) If ammonites were bioluminescent, is there evidence that their ability to choreograph and match the changing bioluminescent patterns of others was a key to group behavior and mating displays?
> No evidence is possible. This is just taken from living squid, very
> distant relatives.
According to Wikipedia, ammonites are phylogenetically closer to coleoids (squids, cuttlefish, and octopi) than are the nautiluses.
Don't nautiluses have changing bioluminescent patterns?
> > (11) Have we found evidence of massive ammonite mating gatherings and that ammonites died shortly after reproduction?
> No, this is just extrapolated from some living cephalopods.
Which ones? if both nautiluses and coleoids are like this, it seems reasonable to infer that ammonites were like this too.
Granted, there is always the possibility of convergent evolution, with the "middle" taxons being more
"conservative" than the extremes. As you know very well, this is true of paleognathic birds, with tinamous being
monophyletic and the ratites being polyphyletic, with convergent features.
Either tomorrow or Friday, I will be posting some interesting details on paleognathic evolution on the thread, "Do birds dream?"
Peter Nyikos
Professor, Department of Mathematics
University of South Carolina -- standard disclaimer --
https://people.math.sc.edu/nyikos/